Downloaded applications can cause the phone to behave unexpectedly or affect the phone performance. Also maybe your phone RAM is full. Remove your memory card and switch ON your phone. if problem persist use safe mode to check if any downloaded application causes the problem. In safe mode, the phone only starts with preinstalled software and applications. If the phone performance improves in safe mode, it’s likely that one or more of the downloaded applications are affecting the phone negatively. You can then uninstall the most recently downloaded application and restart the phone.

To enable safe mode
1.Turn off the device.
2.Press and hold down the power key until the phone vibrates.
3.Wait until the Techno logo disappears.
4. Press and hold the volume down key. The device then restarts in safe mode.